1. Field of the Invention
The present invention relates to a camera diaphragm device in which two diaphragm blades, having diaphragm aperture portions whose diameters differ from each other, are moved to and away from an exposure aperture portion by reciprocatingly rotating the two diaphragm blades by respective driving means.
2. Description of the Related Art
Widespread use of digital cameras has caused more and more recent camera diaphragm devices to be capable of controlling the size of a shooting optical path (diaphragm aperture) in two stages by causing diaphragm blades, having circular diaphragm aperture portions, to move to and away from an exposure aperture portion, which restricts a maximum diaphragm aperture, by driving means such as a motor. However, since the two-stage control operation is not a satisfactory control operation, a camera diaphragm device that can control the size of the shooting optical path in three stages by causing a second diaphragm blade, having a diaphragm aperture portion whose diameter is different from that of the aforementioned diaphragm blades, to move to and away from the exposure aperture portion by second driving means is discussed in Japanese Unexamined Patent Application Publication No. 10-221740 (Patent Document 1).
For the camera diaphragm device discussed in Patent Document 1, when the two diaphragm blades are moved away from the exposure aperture portion, they are accommodated in different areas of a base plate surface. For this reason, in this structure, the area required for accommodating the two diaphragm blades is large, thereby making it very difficult to reduce the size of the base plate, that is, to reduce the size of the device. To overcome this problem, when the two diaphragm blades are moved away from the exposure aperture portion, the two diaphragm blades are accommodated in substantially the same area of the base plate surface, and are configured to move to the exposure aperture portion from substantially the same direction.
Recent digital cameras are becoming very small and come in many designs. Therefore, even in diaphragm devices, the shape of the base plate is considerably restricted, and, for example, the mounting position and the structure of a motor serving as driving means mounted to the base plate are also considerably restricted. Therefore, even if the two diaphragm blades are formed so as to be accommodated in substantially the same area of the base plate surface as mentioned above, it may be necessary to dispose the two diaphragm blades by bringing the mounting positions of the two diaphragm blades with respect to the base plate close to each other.
Even in such a structure, the base plate is required to be smaller. If an attempt is made to reduce the size of the base plate, one of the diaphragm blades may be formed into a shape that does not allow it perform its function by itself. Therefore, even in such a case, a structure that can compensate for this is expected to appear. In addition, the two diaphragm blades are formed so that that they rotate individually at the areas that are close to each other by the respective driving means. Therefore, due to the shapes and mounting positions of the diaphragm blades, in terms of operation, it is necessary to form the diaphragm blades so that one diaphragm blade does not interfere with the driving pin of the other diaphragm blade. Further, when only one of the diaphragm blades is operated, it is easy to determine whether a malfunction has occurred. However, when both of the diaphragm blades are operated, it is difficult to determine whether a malfunction has occurred.